Welding torch

ABSTRACT

The invention describes a welding torch ( 1 ), consisting of a main body ( 2 ) comprising at least one part, in which a feed device ( 10 ) for a welding rod ( 7 ) is disposed and which is joined to a connecting piece ( 21 ) in order to receive a contact pipe ( 23 ). A guide device ( 32 ) for the welding rod ( 7 ) is being disposed in the feed device ( 10 ) extending at an angle in the direction from the connecting piece ( 21 ) into the contact pipe ( 23 ). A bore ( 36 ) for the welding rod ( 7 ) and a guide bore ( 37 ) of a larger diameter ( 40 ) concentric therewith for the guide device ( 32 ) is provided in the contact pipe ( 23 ), the guide device ( 32 ) extending into the guide bore ( 37 ) of the contact pipe ( 23 ).

The invention relates to a welding torch comprising a main body, a feeddevice for a welding rod disposed on the main body and joined to aconnecting piece, and a contact pipe received in the connecting piece,the contact pipe having a guide bore.

The invention relates to a welding torch of the type described in thegeneric part of claims 1 and 2.

Welding torches are already known in which the welding rod is fed to thecontact pipe by means of a feed device. These welding torches consist ofa main body in which a feed device for a welding rod is arranged. Thefeed device is joined to a connecting piece which receives the contactpipe. In order to provide a better guiding action for the welding rod,the feed device, which may consist of a copper pipe for example, housesa guide device. To this end, the guide device is designed to have anexternal diameter smaller than the internal diameter of the feed device.Furthermore, the internal diameter of the guide device more or lesscorresponds to the external diameter of the welding rod so that thewelding rod is accurately guided in the guide device. The guide deviceextends from the hose pack, which is connected to the welding torch, asfar as the contact pipe. The disadvantage of a welding torch of thistype is that because the welding rod is fed flexibly through a flexiblehose pack for the welding rod, it may have a tendency to develop a flexor bend, preventing the welding rod from being introduced automaticallyinto the contact pipe.

The underlying objective of this invention is to provide a welding torchin which the feeding and placing in contact of the welding rod can beimproved.

In a welding torch of the first-described structure, this object isaccomplished with a contact pipe which has a bore for the welding rodand in which the guide bore has a larger diameter and is concentric withthe bore for the welding rod. The welding torch comprises a guide devicefor the welding rod disposed in the feed device and extending into theguide bore of the contact pipe and from the connecting piece in adirection away from the contact pipe, the guide device being comprisedof a flexible, elastically non-conductive material. The advantage ofthis system is that the welding rod is fed through a matching bore ofthe contact pipe producing accurate positioning as it leaves the feeddevice. Another advantage resides in the fact that because the guidedevice provides an, accurate guiding action across the length of thebore in the contact pipe, the welding rod can be straightened, inparticular to remove any bends in the welding rod, so that the weldingrod enters the bore of the contact pipe without kinks, which will atleast reduce friction of the welding rod in the bore of the contactpipe. Also, the flexible guide device can adapt to bending in thewelding rod, thereby ensuring that the welding rod can be easily guidedto the contact pipe without current, thereby preventing any sparking orarcuing in the interior of the welding torch or feed device.

According to another aspect of the invention, a welding torch of thefirst-described structure comprises a bridging piece in the region ofthe connecting piece and projecting into the guide bore of the contactpipe, and a guide device for the welding rod disposed in the feed deviceandextending in the guide bore from the connecting piece in a directionaway from the contact pipe, the guide device being connected to thebridging piece.

A guide bore having a larger diameter than that of the bore for thewelding rod enables the welding rod to be accurately positioned telativeto the contact pipe.

If there is a transition region between the bore for the welding rod andthe guide bore, which has a conical taper, the welding rod emerges fromthe guide device, the welding rod is deflected in a direction towardsthe bore of the contact pipe because of the conical tapered design,enabling the welding rod to be fed along automatically.

Preferably, the bridging piece is composed of several components ofdifferent materials, such as a holder component and a guide component.Such a bridging piece is inexpensive to make since only the parts usedto guide the welding rod need to be made from a high quality material,which is preferably highly resistant to friction.

A guide component projecting into the guide bore of the contact pipeoffers a simple way of positioning the welding rod accurately for thecontact pipe.

If the guide component is preferably threadedly connected to the holdercomponent the guide component of the bridging piece can be readilyadapted to suit different welding rods.

The bridging piece is prevented from moving if the holder component hasa bearing face in a transition region to the guide component.

The advantage of at least a part of the holder component projecting intothe feed device is that the radius of the guide device as it emergesfrom the feed device is not too small, since it would otherwise beimpossible to feed the welding rod to the contact pipe automatically.

If the holder component and the guide device are threadedly connected,the guide device is prevented from working loose from the bridging piecedue to pulling and pushing movements of the welding rod.

Resistance can be kept low as the wire is fed through a guide devicewhich has an external diameter preferably 10% to 50% smaller than theinternal diameter of the feed device, which is a copper pipe, and aninternal diameter at least slightly larger than an external diameter ofthe welding rod.

A reliable contact of the welding rod with the contact pipe, enabling atransfer of current into the contact pipe, is obtained if the contactpipe bore has a diameter that is slightly larger than an externaldiameter of the welding rod.

When the welding torch is used with a welding robot, it can be dulypositioned to reach weld spots that are not readily accessible if themain body has a curved end section.

The welding time for a welding process can be significantly increased ifa cooling device consisting of at least two coolant supply lines isdisposed in the main body.

Preferably, the feed device is connected to a source of an inert gas,the feed device and the connecting piece having radially aligned boresin a transition region between the connecting piece and an end region ofthe feed device so that an inert gas atmosphere is produced within thewelding torch or contact pipe, preventing corrosion of the welding torchand its individual components.

The welding rod may be made of a soft metallic material so that, byusing the bridging piece in conjunction with an aluminum welding rodhaving a low natural stiffness, the welding rod can be duly positionedor aligned.

The invention will be described below with reference to examples ofembodiments illustrated in the accompanying drawings. Of these:

FIG. 1 is a simplified schematic diagram of the welding torch proposedby the invention, shown in cross section from a side view;

FIG. 2 is a simplified schematic diagram of a cross section of anotherembodiment of the welding torch proposed by the invention, seen from aside view;

FIG. 3 is a simplified diagram illustrating details of the bridgingpiece, seen in cross section from a side view;

FIG. 4 is a simplified schematic diagram showing an example of adifferent design which may be used for the bridging piece in the weldingtorch proposed by the invention;

FIG. 5 is a simplified schematic diagram of another embodiment of thebridging piece which may be used with the welding torch proposed by theinvention;

FIG. 6 is a simplified schematic diagram of another embodiment of thebridging piece.

Firstly, it should be pointed out that the same parts of the differentembodiments described are denoted by the same reference numerals or samecomponent names, which means that disclosures made throughout thedescription can be transposed in terms of meaning to the same parts withthe same reference numerals or component names. The positions referredto in the description, such as top, bottom, side, etc., relate to thedrawing specifically being described and, when a different position isbeing described, can be transposed in terms of meaning to the newposition. Furthermore, individual features from the different examplesof embodiments illustrated, may deemed to represent solutions proposedby the invention in their own right.

FIG. 1 illustrates a welding torch 1, which might be used for MIG/MAGwelding for example, the welding torch 1 in the embodiment illustratedbeing designed for a welding robot.

The welding torch 1 consists of a main body 2, which may be made from asingle component but preferably consists of several parts. In theembodiment illustrated, the main body 2 consists of a connecting piece3, a middle piece 4 and an end piece 5. The individual parts of the mainbody 2 are made from brass, for example, and are either welded togetheror joined to one another by means of individual beads 6. Clearly, itwould also possible for any other material to be used for the main body2. The main body 2 could also have an insulating layer on its externalsurface in the form of a plastics material.

By means of the connecting piece 3, the welding torch 1 can be connectedto a hose pack on a welding device or a current source. The hose pack isused to supply the various additional materials needed for the weldingtorch 1 such as a welding rod 7, an inert gas 8 and a coolant fluid forcooling the welding torch 1, for example. The welding torch 1 is alsosupplied with energy via the hose pack, in particular with current andvoltage, drawn from the welding device or from the power source.

An insulating layer 9 made from a plastics material for example may beprovided inside the main body 2. The purpose of the insulating layer 9is to isolate the current flowing in the interior of the welding torch 1from the external surface, in other words from the main body 2, so thatthe user will not be subjected to an electric shock if he touches thewelding torch 1.

The welding torch 1 also has a feed device 10 inside the main body 2,which is made up of a copper pipe 11 and a bridging element 12. The feeddevice 10 is connected to the connecting piece 3 at one end and to theend piece 5 of the main body 2 at the other end. The copper pipe 11 andthe bridging element 12 of the feed device may be joined to theconnecting piece 3 and/or the end piece 5 by means of a push-fit,soldering or welding.

The bridging element 12 has a bore 13 running through its centre. In theembodiment of the welding torch 1 illustrated, the bore 13 is arrangedin the longitudinal direction of a longitudinal central axis 14 runningthrough the centre of the welding torch 1. Adjoining the bridgingelement 12 in the direction of the connecting piece 3, the copper piper11 is connected to the bridging element 12, the copper pipe 11 beingconnected to the bridging element 12 in such a way that a cavity 15disposed in the interior of the copper pipe 11 runs concentrically or isaligned with the bore 13 of the bridging element 12, i.e. the copperpipe 11 has an internal diameter 16 which matches the diameter of thebore 13 of the bridging element 12. The copper pipe 11 may be solderedto the bridging element 12, for example, or may joined to the bridgingelement 12 by means of a bead 17.

In the embodiment illustrated, the copper pipe 11 is designed so that itextends from the middle region, in other words in the longitudinaldirection of the longitudinal central axis 14 of the welding torch 1, atan angle in a direction towards the interior face of the main body 2,after which the copper pipe 11 runs parallel with the middle piece 4, inparticular parallel with the insulating layer 9, i.e. the copper pipe 11bends or deflects from the centre position, in particular from theposition running along the longitudinal central axis 14 extending in alongitudinal direction, into a position running parallel with thelongitudinal central axis 14.

As a result of the bend or deflection from the centre position of thewelding torch 1 to a position or point running parallel with thelongitudinal central axis 14, a free space is formed inside the mainbody 2 enabling a cooling device 18 to be arranged in the interior ofthe main body 2. The cooling device 18 comprises supply pipes 19,although only one of these supply pipes 19 is illustrated in the crosssection shown here. By disposing the cooling device 18 in the interiorof the main body 2, a coolant can be duly pumped or conveyed through thesupply pipe 19 into the interior volume of the welding torch 1, whichcan then be fed back out of the welding torch 1 by supply pipes 19 notillustrated. The welding torch 1 can be cooled using a circuit design ofthis type.

Clearly, it would also be possible for the feed device 10 to extend inthe longitudinal direction of the welding torch 1, in other wordsaligned with the longitudinal central axis 14, in which case theindividual supply pipes 19 may be arranged parallel with thelongitudinal central axis 14.

Provided in an end region 20 of the welding torch 1, in other words inthe region of the end piece 5, is a connecting piece 21 disposed in thedirection opposite the connecting piece 3. The connecting piece 21 isconnected to the bridging element 12 of the feed device 10. To this end,the bridging element 12 may be joined to the connecting piece 21 bymeans of a thread fitting 22, in which case the bridging element 12 willhave an external thread and the connecting piece 21 will have aninternal thread so that the connecting piece 21 can be screwed onto thebridging element 12. The purpose of the connecting piece 21 is toreceive a contact pipe 23 which will be needed for a welding process. Tothis end, the connecting piece 21 also has a thread fitting 24 by meansof which the contact pipe 23 can be connected or attached to theconnecting piece 21. By using a thread fitting 24 to connect the contactpipe 23, the contact pipe 23 can easily be exchanged by the user withoutthe need for an engineer to be present.

In the welding torch 1 illustrated, the inert gas 8 used to produce aninert gas shield in the region of the weld spot is fed via the feeddevice 10, i.e. the inert gas 8 is fed from the connecting piece 3 viathe copper pipe 11 in a direction towards the end region 20 of thewelding torch 1, so that an inert gas shield can be produced at thewelding point as it leaves the feed device 10. To this end, the bridgingelement 12 has bores 25 running radially around the longitudinal centralaxis 14 of the welding torch 1 in the end region 20 of the welding torch1. Furthermore, a cavity 26 is provided in the connecting piece 21 sothat the inert gas 8 can flow from the feed device 10, in particularfrom the bridging element 12, through the bores 25 into the cavity 26 ofthe connecting piece 21. To ensure that the inert gas 8 is able to flowfrom the cavity 26 to the welding point, the connecting piece 21 in isin turn provided with bores 27 running radially around the longitudinalcentral axis 14. The bores 27 are disposed in the region of the cavity26 on the connecting piece 21 so that the inert gas 8 can flow from thecavity 26 through the bores 27 and out to the welding point.

In order to concentrate the inert gas 8 around the contact pipe 23 or onthe welding point, the welding torch 1 has a gas nozzle 28. The gasnozzle 28 is connected to the end piece 5 of the main body 2 and the gasnozzle 28 may be provided with a thread to provide a connection to theend piece 5. Clearly, it would also be possible for the gas nozzle 28 tobe fitted to the end piece 5 of the main body 2 by a simple push-fitarrangement. The gas nozzle 28 is arranged so that the inert gas 8delivered collects in the interior 29 of the gas nozzle 28 and thenflows in the direction of the contact pipe 23, so that an inert gasatmosphere is formed around the contact pipe 23 or the welding point.For this purpose, it would be possible to provide an insulating cap 30over the connecting piece 21, for example. The insulating cap 30 in turnhas bores 31 running radially in the region of the bores 27 of theconnecting piece 21. The inert gas 8 is able to flow through these bores31 from the feed device 10 via the individual bores 25, 27, 31 into theinterior 29 of the gas nozzle 28, forming an atmosphere of inert gasaccordingly.

The advantage of directing the inert gas 8 through the feed device 10resides in the fact that in addition to the inert gas 8 flowing out fromthe bores 25, 27, 31, inert gas 8 is also able to flow through thecontact pipe 23 in the direction of the weld spot, again building up aninert gas atmosphere in the interior of the contact pipe and hencepreventing any corrosion of the contact pipe 23.

Clearly, it would also be possible to deliver the inert gas 8 by meansof additional lines so that an inert gas atmosphere can also be formedin the region of the contact pipe 23.

To enable the welding rod 7 to be fed through the welding torch 1, aguide device 32 for the welding rod 7 is provided in the feed device 10.The guide device 32 is made from an elastic pipe or a coil spring, forexample, made from a plastics material. Clearly, it would be possible touse any material exhibiting elastic properties. It would also bepossible for the guide device 32 to be made from an electricallynon-conductive material, which would allow the welding rod 7 to be fedas far as the welding torch 1 without current. Moreover, the guidedevice 32 has an external diameter 33 that is smaller or less than theinternal diameter 16 of the feed device 10, in particular of the copperpipe 11. In this respect, the external diameter 33 of the guide device32 may be 10% to 50%, preferably 25% smaller than the internal diameter16 of the feed device 10.

An internal diameter 34 of the guide device 32 is at least slightlylarger than an external diameter 35 of the welding rod 7. By using adesign of this type, the guide device 32 can be pushed inside the copperpipe 11 and in the feed device 10. At the same time, the welding rod 7can be readily conveyed due to the matching layout of the internaldiameter 34.

The advantage of this arrangement of guide device 32 is that a weldingtorch 1 of this type is used for various welding processes requiring theuse of different welding rods 7 of varying external diameters 35, whichmeans that a feed device 10 which can not be removed will have to bedimensioned accordingly, particularly in terms of its internal diameter16. With this system, the user of the welding torch 1 will merely haveto change the guide device 32 in order to adapt to the most varied ofwelding rods 7. Clearly, several welding rods 7 of differing externaldiameters 35 could be used with an appropriate guide device 32 having amatching internal diameter 34.

In practice, if no guide device 32 were inserted in the feed device 10,faults could occur when inserting or introducing the welding rod 7 inthe direction of the contact pipe 23 because of the relatively largeinternal diameter 16 of the feed device 10 since a large internaldiameter 16 of the feed device 10 could cause the welding rod 7 to runor bend accordingly, causing the welding rod 7 to kink in the weldingtorch 1, thus preventing an automatic feed of the welding rod 7.

The guide device 32 is arranged in the welding torch 1 in such a waythat it extends from the connecting piece 3 and the hose pack throughthe feed device 10, in particular through the copper pipe 11 and thebridging element 12, in a direction towards to the contact pipe 23. Thisbeing the case, the contact pipe 23 is designed so that a bore 36 isprovided for the welding rod 7 and a guide bore 37 for the guide device32. The guide bore 37 for the guide device 32 extends across a length 38from the bridging element 12 in the direction of the bore 36, inparticular from the bridging element 12 to the weld point. Thedifference between the bores 36 and the guide bore 37 of the contactpipe 23 resides in the fact that the bore 36 for the welding rod 7 has adiameter 39 which is slightly larger than the external diameter 35 ofthe welding rod 7. The diameter 40 of the other guide bore 37 of thecontact pipe 23 for the guide device 32 is slightly larger than theexternal diameter 33 of the guide device 32. As a result, the guidedevice 32 can be inserted in or pushed into the guide bore 37 of thecontact pipe 23 so that the guide device 32 can be accurately positionedrelative to the contact pipe 23 across the length 38.

In addition, in a transition region 41 to the bore 36, the guide bore 37has a conical taper 42 so that there are no sharp edges as the weldingrod 7 emerges from the guide device 32 and is transferred to the bore 36of the contact pipe, enabling the welding rod 7 to be fed inautomatically.

Because of the positioning of the guide device 32 or the insertion ofthe guide device 32 in the contact pipe 23, the welding rod 7 can beexactly positioned across the length 38 to the bore 36 of the contactpipe 23, i.e. the internal diameter 34 of the guide device 32 is keptpositioned flush with or in alignment with the bore 36 of the contactpipe 23 and the welding rod 7 can be fed or conveyed accurately from theguide device 32 to the bore 36 of the contact pipe 23. This arrangementof the guide device 32 also means that if the guide device 32 is madefrom an elastic, non-electrically conductive material, such as plasticsfor example, the current will not cross over until the region of thecontact pipe 23. This is an advantage in that if there is sparking orarcing, there will be no loss of power due to the short length of thewelding rod 7 across which energy is carried.

Clearly, it would also be possible for the current to be conveyed withthe welding rod 7 actually in the welding torch 1, in other words in thefeed device 10. It would also he conceivable to apply energy to thewelding rod 7 as far back as the welding device or at the current sourceso that current would be carried from the welding device to the weldingtorch 1 through the welding rod 7.

Another advantage of designing the welding torch 1 so that the guidedevice 32 is positioned in the contact pipe 23, particularly if theguide device 32 is inserted in the guide bore 37 of the 3contact pipe23, is that when using a welding rod 7 made from a readily deformablematerial, as would be the case with an aluminium welding wire forexample, the welding rod 7 would be susceptible to kinks as it is fedthrough the hose pack which would make it impossible to feed or weldwithout being able to position the welding rod 7 exactly as it emergesfrom the guide device 32 and enters the bore 36 of the contact pipe 23since sharp edges could be formed if the differences in the diameters ofthe individual components were too great.

In the embodiment as illustrated in FIG. 1, the individual components ofthe welding torch 1 are preferably rounded.

FIG. 2 illustrates another embodiment of the welding torch 1 proposed bythe invention. In this embodiment, only the end region 20 of the weldingtorch 1 is illustrated. In this case, the welding torch 1 is bent orangled, i.e. the middle piece 4 of the main body 2 has a radius 43 inthe region 20 of the welding torch 1.

The welding torch 1 is of the same construction as that illustrated inFIG. 1 but no insulating layer 9 is provided between the main body 2 andthe feed device 10, in particular the copper pipe 11. The welding torch1 essentially consists of the same components but the shape of theindividual components may be different, i.e. the welding torch 1comprises the feed device 10, consisting of the copper pipe 11 and thebridging element 12, as well as the connecting piece 21 and the contactpipe 23 joined to the connecting piece 21. As illustrated, the gas inthis embodiment is again delivered to the welding torch 1 via the feeddevice 10 and accordingly the bores 25 in the bridging element 12 areradially disposed and the bores 27 in the connecting piece 21 areradially disposed relative to the longitudinal central axis 14 of thewelding torch 1 so that the inert gas 8 can escape through the bores 25,26 and the bore 31 of the insulating cap 30. The inert gas 8 is thencollected by means of the gas nozzle 28 in the welding region, in otherwords around the contact pipe 23, therefore forming an inert gasatmosphere in the welding region.

The only difference as compared with the embodiment illustrated in FIG.1 is that the guide device 32 is not inserted in the guide bore 37 ofthe contact bush 23 as illustrated in FIG. 1 but instead a bridgingpiece 44 is arranged between the guide device 32 and the contact bush23. The bridging piece 44 may be made in one piece although the bridgingpiece 44 in the embodiment illustrated is made from two parts. In thiscase, the bridging piece 44 has a holder component 45 and a guidecomponent 46.

The bridging piece 44 is designed so that the guide device 32 projectsinto the holder component 45, the guide component 46 in this case beingpositioned in the guide bore 37 of the contact bush 23. The bridgingpiece 44, in particular the holder component 45, projects, at leastacross a part, into the guide device 10 of the welding torch, producinga firm seat for the holder component 45 on the feed device 10. For thispurpose, the bridging piece 44, in particular the holder component 45and the guide component 46, are designed to have different bores, on theone hand for the guide device 32 and on the other hand for the weldingrod 7. The bridging piece 44 will be described in more detail withreference to FIG. 3.

The purpose of the bridging piece 44 is to ensure that the welding rod 7is accurately positioned relative to the contact bush 23, in particularrelative to the bore 36 of the contact bush 23. The advantage of thedesign used for the bridging piece 44 resides in the fact that thewelding rod 7, which is fed through the feed device 32 into the guidecomponent 46 of the bridging piece 44, is duly aligned by means of thisguide component 46, i.e. the welding rod 7 becomes duly misalignedbecause of the radius 43 of the welding torch 1 and the flexibly runningguide device 32 and the welding rod 7 is then straightened or re-alignedby means of the guide component 46 so that it can enter the bore 36 ofthe contact pipe 23 with relatively little misalignment.

For this reason, the guide component 46 may have a conical taper 42 inthe transition region 41 between the holder component 45 and the guidecomponent 46, i.e. the guide component 46 has a conical taper 42 sothat, as the welding rod 7 leaves the guide device 32 and enters thebore of the guide component 46, the welding rod is deflected by means ofthe conically extending taper 42 in the direction of the bore of theguide component 46 so that it can enter the guide component 46 withoutgiving rise to any problems.

If the bridging piece 44 is made from two parts, the holder component 45may be made from copper whilst the guide component 46 may be made fromwear-resistant materials. The guide component 46 may be made from anelectrically non-conductive, highly friction-resistant material, forexample, so that there is no wear on the guide component 46 and thewelding rod 7 is not damaged due to the action of aligning the weldingrod 7 in the guide component 46. Another advantage of using a guidecomponent 46 made from a non-conductive material is that current orenergy is not applied to the welding rod 7 until it reaches the contactpipe 23, preventing any short-circuiting in the region of the guidecomponent 46 or in the welding torch 1.

FIG. 3 illustrates a side view of the bridging piece 44 in crosssection. The bridging piece 44 again comprises the holder component 45and the guide component 46.

As may be seen from FIG. 3, the bridging piece 44 has a guide bore 47with a diameter 48. The holder component 45 is also provided with athread fitting 49 across a part-region of the guide bore 47 or acrossthe entire guide bore 47, in particular an internal thread.

The guide component 46 is provided in the form of a tubular member andalso has a thread across a part-region of its length 50 so that theguide component 46 can be screwed into the guide bore 47 of the holdercomponent 45. The guide component 46 in turn has a bore 51 in thelongitudinal direction of the bridging piece 44 with a diameter 52 butthe diameter 48 of the guide bore 47 for the guide device 32 is largerthan the diameter 52 of the bore 51 in the bridging piece 44 for thewelding rod 7. Providing the thread fitting 49 means that the bridgingpiece 44 can be made from various materials. In this respect, it ispreferable if the holder component 45 is made from copper and the guidecomponent 46 is made from a highly friction-resistant, preferablynonconductive material.

In the transition region between the holder component 45 and the guidecomponent 46, the bridging piece 44 also has a raised portion 53, inparticular a bearing face 54. The purpose of the bearing face 54 is thatwhen the bridging piece 44 is positioned on the bridging element 12, thelatter is able to penetrate the bore 13 of the bridging element 12 bymeans of the holder component 45, in particular by means of the externalface of the holder component 45, so that the bearing face 54 providessupport for the bridging piece 44. At the same time, the bearing face 54has another function in that when the welding rod 7 is being displacedin the direction of the contact pipe 23, the bearing face 54 bearsagainst the contact pipe 23 preventing the guide component 46 frompenetrating the guide bore 37 of the contact bush 23 too far.

The bridging piece 44, in particular the diameter 48 of the guide bore47 of the holder component 45, is so dimensioned that the guide device32 is able to penetrate the guide bore 47 of the holder component 45 sothat a firm seat is provided for the holder element 45 and the bridgingpiece 44 on the guide device 32. The diameter 52 of the bore 51 of theguide component 46 is designed to be slightly larger than the externaldiameter 35 of the welding rod 7 so that as the welding rod 7 enters thebore 51 of the bridging piece 44, the welding rod 7 is alignedaccordingly.

The alignment of the welding rod 7 can be controlled as a result of thedimensions of the length 50 of the guide component 46, i.e. due to thelength 50 of the guide component 46, the welding rod 7 can be variablyaligned so that a longer length 50 of the welding rod 7 can bere-aligned than would be the case if the guide component 46 were of ashorter length 50.

Clearly, it would also be possible for the bridging piece 44 to be ofany shape. For example, the bridging piece 44, in particular the holdercomponent 45, might have two different guide bores 47, in which case oneguide bore 47, in particular the guide bore 47 in which the guide device32 is inserted, will have a diameter 48 matching the external diameter33 of the guide device 32. The other guide bore 47 may be of a largerdiameter 48, for example, so that the guide component 46 may be largerin size. To do this, however, the guide bore 37 must be adapted to theappropriate diameter of the guide component 46 at the contact bush 23.

FIGS. 4 and 5 illustrate another embodiment of the welding torch 1 withthe bridging piece 44. In the embodiment illustrated here, only thecontact pipe 23 connected to the bridging piece 44 and the connectionbetween the bridging piece 44 and the bridging element 12 are shown.

As may be seen more clearly from FIG. 4, the guide device 32 is insertedin the guide bore 47 of the holder component 45. For this purpose, aninternal thread may be provided in the guide bore 47, for example, bymeans of which the guide device 32 can be screwed onto a thread arrangedon its external circumference. By connecting the guide device 32 to thebridging piece 44 by means of a thread fitting, the guide device 32 canbe firmly seated on the holder component 45, preventing the guide device32 and the bridging piece 44 from coming loose of their own accord asthe welding rod 7 is subjected to pushing movements or if the weldingrod 7 is pulled. The guide component 46 is in turn screwed into theguide bore 47 of the holder component 45 by means of the thread fitting49, the cross section of the guide for the welding rod 7 being reduced,i.e. a transition is provided in the guiding action of the welding rod 7between the internal diameter 34 of the guide device 32 and the diameter52 of the bore 51 of the guide component 46. Reducing the cross sectionensures that any misalignment occurring as the welding rod 7 is fedacross the length 50 of the guide component 46 is redressed, i.e. thewelding rod 7 is re-aligned across the length 50 ensuring that thewelding rod 7 is fed accurately into the bore 36 of the contact pipe 23.

To provide a smooth transition from the internal diameter 34 of theguide device 32 to the diameter 52 of the bore 51 of the guide component46, the end region of the guide component 46, in other words the contactregion between the guide component 46 and the guide device 32, isprovided with a taper 55 running conically relative to the longitudinalcentral axis 14 of the welding torch 1. This results in an edge-freetransition to the guide component 46 as the welding rod 7 is fed out ofthe guide device 32 so that, as it arrives at the taper 55, the weldingrod 7 is steered automatically or of its own accord into the bore 51 ofthe guide component 46, after which the welding rod 7 is aligned orstraightened across the length 50 of the guide component 46.

The dimension of the diameter 52 of the bore 51 of the guide component46 is such that it acts to adjust, in particular align the welding rod7, i.e. the size of the diameter 52 relative to the external diameter 35of the welding rod 7 can be used as a means of predetermining thealignment of the welding rod 7, thereby ensuring that in the contactpipe 23, the welding rod 7 will make perfect contact with the surface ofthe bore 36 of the contact pipe 23 ensuring that current will passthrough in the region of the contact pipe 23.

FIG. 5 illustrates another field of application and another embodimentof the bridging piece 44. The guide device 32 is again inserted in theholder component 45 but in this case the holder component 45 is notscrewed in as illustrated in FIG. 4 but is connected to the guide device32 by a push-fit, again producing a firm and solid seat between theguide device 32 and the holder component 45. In the embodimentillustrated in FIG. 5, the guide component 46 is designed to have anappropriate length 50 for aligning the welding rod 7, this length 50being such that it can impart an aligning action to the welding rod 7.

In this case, the diameter 52 of the bore 51 of the guide component 46is not the decisive means by which the guide component 46 aligns thewelding rod 7, as was the case with the embodiment illustrated in FIG.4, and instead the length 50 of the guide component 46 effects thealignment of the welding rod 7, i.e. because the welding rod 7 is fed inthe guide component 46 over a longer stretch and more accurately, thewelding rod 7, in particular the alignment of the welding rod 7, iscorrected so that as the welding rod 7 leaves the guide component 46 itfollows an almost straight course allowing it to be accurately fedthrough the bore 36 of the contact pipe 23.

In this embodiment, however, the cross section is also reduced as ameans of adjusting the course of the welding rod 7, i.e. the internaldiameter 34 of the guide device 32 is reduced to a diameter 52 the sameas the bore 51 although the bore 51 and its diameter 52 do not have tomatch the external diameter 35 of the welding rod 7 exactly since thealigning or straightening action is imparted to the welding rod 7 acrossthe corresponding length 50 of the guide component 46 so that a bridgingpiece 44 can be inserted to cater for different welding rods 7 ofdiffering external diameters 35, for example.

The embodiments described above in respect of FIGS. 4 and 5 may be usedfor welding rods 7 which have an inherently high degree of stiffness orfor a welding rod 7 made from a slightly flexible material with a lownatural stiffness, as is the case with an aluminium welding rod, forexample. With welding rods 7 of this type, the process of feeding fromthe welding rod roll to the welding torch 1 via the hose pack and thenthrough the guide device 32 to the contact pipe 23 imparts a kink to thewelding rod 7 accordingly because the welding rod 7 tends to conform tothe flexing variations in the hose pack and the guide device 32 as wellas the angled design of the welding torch 1 as it passes through thehose pack.

Providing the bridging piece 44 has an advantage because inserting thebridging piece 44 aligns the welding rod 7 before it is fed into thecontact bush 23, thereby ensuring that the welding rod 7 is accuratelypositioned and guided. Another advantage is to be gained if the guidedevice 32 is made from a non-conductive material and the bridging piece44 is made in two parts, the guide component 46 being made from anon-conductive material, because the welding rod feed requires nocurrent and current will not pass into the welding rod 7 until it entersthe contact pipe 23 or leaves the contact pipe 23, preventing any lossesin power which would occur if the current were fed via the welding rod7. Another advantage of feeding the welding rod 7 to the contact pipe 23without current is that sparking can be avoided in the interior of thewelding torch 1 and in the hose pack, preventing the welding rod 7 fromfusing in the interior of the welding torch 1, which means that awelding process can be applied for a longer period using a welding torch1 of this type.

Clearly, it would also be possible to use a welding torch 1 of thisdesign as a hand-welder, i.e. the bridging piece 44 and the guide device32 feeding into the contact pipe 23 can also be used with a hand-welder.

FIG. 6 illustrates another embodiment of the bridging piece 44 in crosssection from a side view. As described with reference to FIGS. 4 and 5,only the key components used to connect the bridging piece 44 to thecontact pipe 23 and the guide device 32 are illustrated.

In the embodiment illustrated here, the bridging piece 44 is not made ofjust two parts but consists of several parts, in particular three parts,and again a connection is provided for the guide device 32 of the holdercomponent 45. The guide component 46 is again inserted in or screwedinto the holder component 45, the cross section being reduced from theguide device 32 to the guide component 46, i.e. there is a reduction incross section from the internal diameter 34 of the guide device 32 to adiameter 52 of the bore 51 of the guide component 46.

Another guide component 56 is then connected to the guide component 46by means of an external thread, for example. The guide component 56 inturn has a bore 57 extending in the longitudinal direction of thewelding torch 1 and the bore 51 of the guide component 46, with adiameter 58. The diameter 58 of the bore 57 is smaller than the diameter52 of the bore 51, producing a further reduction in the cross sectionguiding the welding rod 7.

In order to ensure a friction-free or edge-free transition from the bore51 to the bore 57, a conically extending taper 59 may be provided in thetransition region from the guide component 46 to the guide component 56.The contact pipe 23 is then arranged adjoining the guide component 56,i.e. this time it is the guide component 56 which is placed or insertedin the guide bore 37 of the contact pipe 23 to provide accurate guidancefrom the exit of the bore 57 of the guide component 56 to the contactpipe 23.

In the embodiment illustrated, the cross section is adapted in a steppeddesign in order to guide the welding rod 7 onto the bore 36 of thecontact bush 23, i.e. the stepped reduction in cross section aligns thewelding rod 7 across the bridging piece 44.

Another advantage of adapting the cross section to the bore 36 using astepped design is that if using different welding rods 7 of varyingexternal diameters 35, it is not necessary to change the entire bridgingpiece 44 to use a different welding rod 7 of another external diameter35 and instead only guide component 56 needs to be replaced in order toadapt to the different external diameter 35 of the welding rod 7.

By pre-aligning the welding rod 7 by means of the guide component 46,the guide component 56, in particular the bore 57, used to provideaccurate alignment of the welding rod 7, can be of a length 60 which isshorter than the length 50 of the guide component 46. This is possiblebecause the welding rod 7 has already been pre-aligned across the length50 of the guide component 46 and only a short length 60 will be neededto ensure perfect positioning.

As with the drawings described above, the bridging piece 44 may be madefrom a single piece rather than providing a bridging piece 44 made fromseveral individual parts.

Clearly, instead of the bridging piece 44, the guide device 32 couldhave an internal diameter 34 of the guide device 32 that is reduced incross section at the end region, in other words in the transition regionto the contact pipe 23, the welding rod 7 again being aligned by meansof this taper. For this purpose, to provide a tapering design of theguide device 32, this piece, in other words the tapered piece, could bepushed into the contact pipe 23, in which case the guide bore 37 wouldmatch the diameter of the guide device 32.

If the guide device 32 is made from a plastics material in thetransition region to the contact pipe 23, it would also be possible toprovide a metal sheath so that the guide device will run in a straightline in the area where the metal sheath is pushed onto the guide device32 in order to align the welding rod 7 in this region.

Finally, for the sake of good order, it should be pointed out that theindividual components and groups of components illustrated in thedrawings are shown out of proportion and on a distorted scale in orderto provide a clearer understanding of the invention.

Above all, the individual embodiments illustrated in FIGS. 1; 2; 3; 4;5; 6 represent independent solutions to the invention in their ownright. The objectives sought by the invention and the solutions proposedcan be found in the detailed description of these drawings.

List of Reference Numerals

1 welding torch

2 main body

3 connecting piece

4 middle piece

5 end piece

6 bead

7 welding rod

8 inert gas

9 insulating layer

10 feed device

11 copper pipe

12 bridging element

13 bore

14 longitudinal central axis

15 cavity

16 internal diameter

17 bead

18 cooling device

19 supply pipe

20 end region

21 connecting piece

22 thread fitting

23 contact pipe

24 thread fitting

25 bore

26 cavity

27 bore

28 gas nozzle

29 interior

30 insulating cap

31 bore

32 guide device

33 external diameter

34 internal diameter

35 external diameter

36 bore

37 guide bore

38 length

39 diameter

40 diameter

41 transition region

42 taper

43 radius

44 bridging piece

45 holder component

46 guide component

47 guide bore

48 diameter

49 thread fitting

50 length

51 bore

52 diameter

53 raised portion

54 bearing face

55 taper

56 guide compartment

57 bore

58 diameter

59 taper

60 length

What is claimed is:
 1. A welding torch comprising (a) a main body, (b) afeed device for a welding rod disposed in the main body and joined to aconnecting piece, (c) a contact pipe received in the connecting piece,the contact pipe having (a) a bore for the welding rod and (b) a guidebore of a larger diameter and concentric with the bore for the weldingrod, and (d) a guide device for the welding rod disposed in the feeddevice and extending into the guide bore of the contact pipe and fromthe connecting piece in a direction away from the contact pipe, theguide device being comprised of a flexible, electrically non-conductivematerial.
 2. The welding torch of claim 1, wherein a transition regionbetween the bore for the welding rod and the guide bore has a conicaltaper.
 3. The welding torch of claim 1, wherein the guide device iscomprised of a plastics material or a material with elastic properties.4. The welding torch of claim 1, wherein the feed device is a copperpipe.
 5. The welding torch of claim 1, wherein the guide device has anexternal diameter smaller than an internal diameter of the feed deviceand an internal diameter at least slightly larger than an externaldiameter of the welding rod.
 6. The welding torch of claim 5, whereinthe external diameter of the guide device is 10% to 50% smaller than theinternal diameter of the feed device.
 7. The welding torch of claim 1,wherein the contact pipe bore has a diameter that is slightly largerthan an external diameter of the welding rod.
 8. The welding torch ofclaim 1, wherein the main body has a curved end section.
 9. The weldingtorch of claim 1, comprising a cooling device consisting of at least twocoolant supply lines disposed in the main body.
 10. The welding torch ofclaim 1, wherein the feed device is connected to a source of an inertgas, the feed device and the connecting piece having radially alignedbores in a transition region between the connecting piece and an endregion of the feed device.
 11. The welding torch of claim 1, wherein thewelding rod is made of a soft metallic material.
 12. A welding torchcomprising (a) a main body, (b) a feed device for a welding rod disposedin the main body and joined to a connecting piece, (c) a contact pipereceived in the connecting piece, the contact pipe having a guide bore,(d) a bridging piece in the region of the connecting piece andprojecting into the guide bore of the contact pipe, and (e) a guidedevice for the welding rod disposed in the feed device and extending inthe guide bore from the connecting piece in a direction away from thecontact pipe, the guide device being connected to the bridging piece.13. The welding torch of claim 12, wherein the bridging piece has a borefor the welding rod and a guide bore for the guide device.
 14. Thewelding torch of claim 13, wherein the guide bore has a diameter that islarger than a diameter of the bore for the welding rod.
 15. The weldingtorch of claim 13, wherein a transition region between the guide borefor the guide device and the bore for the welding rod has a conicaltaper.
 16. The welding torch of claim 12, wherein the bridging piece iscomposed of several components.
 17. The welding torch of claim 16,wherein the bridging piece comprises a holder component and a guidecomponent.
 18. The welding torch of claim 17, wherein the holdercomponent and the guide component are made of different materials. 19.The welding torch of claim 17, wherein the guide component projects intothe guide bore of the contact pipe.
 20. The welding torch of claim 19,wherein the guide bore has a diameter that is slightly larger than anexternal diameter of the guide component.
 21. The welding torch of claim17, wherein the guide component has a diameter that is slightly largerthan an external diameter of the welding rod.
 22. The welding torch ofclaim 17, wherein the guide component is connected to the holdercomponent.
 23. The welding torch of claim 22, wherein the guidecomponent is threadedly connected to the holder component.
 24. Thewelding torch of claim 17, wherein the holder component has a bearingface in a transition region to the guide component.
 25. The weldingtorch of claim 17, wherein at least a part of the holder componentprojects into the feed device.
 26. The welding torch of claim 17,wherein the holder component and the guide device are threadedlyconnected.